In this era of modernization, electricity has become the cup of life. A moment without electricity makes your thinking go dry. The major source of conventional form of electricity is through wires. The continuous research and development has brought forward a major breakthrough, which provides electricity without the medium of wires. This wonder baby is called Witricity. There are certain small but very useful discoveries made in history, which changed the world forever, Newton’s gravitational law, Watt’s steam engine, Thomson’s bulb and many more.
But a renaissance occurred with the invention of Electromagnetic Waves by Maxwell. Sir Jagdish Chandra Bose successfully generated electromagnetic waves having wavelength in the range of 5mm to 25 mm. Thereafter an Italian scientist named Marconi succeeded in transmitting electromagnetic waves up to a distance of several miles. And with this there started a new era called WIRELESS TECHNOLOGY.
Today, as we can see the word ‘wireless’ is common in day – to – day life.
Wireless communication has made the world smaller. Almost each and everything is wireless or cordless. Cordless mouse, cordless keyboard, satellite communication, mobiles, cordless microphones and headphones, wireless internet service i.e. WI-FI, etc. And these have definitely increased the standard of living. In fact it dates back to the 19th century, when Nikola Tesla used conduction-based systems instead of resonance magnetic fields to transfer wireless power. As it is in Radiative mode, most of the Power was wasted and has less efficiency. Further, in 2005, Dave Gerding coined the term WiTricity which is being used by the MIT researchers today.
Moreover, we all are aware of the use of electromagnetic radiations which is quite well known for wireless transfer of information. In addition, lasers have also been used to transmit energy without wires.
However, radio waves are not feasible for power transmissions because the nature of the radiation is such that it spreads across the place, resulting into a large amount of radiations being wasted. Witricity is based upon coupled resonant objects to transfer energy between objects without wires. The system consists of a Witricity transmitter, and devices which act as receivers. Like radio receivers, the devices must be in range of the transmitter. Witricity will ensure that the cell phones, laptops, iPods and other power thirsty devices get charged on their own, eliminating the need of plugging them in. Even better, because of Witricity some of the devices won’t require batteries to operate which is a boon for the users of these devices.
In 1825 William Sturgeon invented the electromagnet, a conducting wire wrapped around an iron core. The principle of EM induction — that a changing magnetic field can induce an electrical current in an adjacent wire — was discovered by Michael Faraday in 1831. Combining these two discoveries, Nicholas Joseph Callan was the first to demonstrate the transmission and reception of electrical energy without wires. Callan’s 1836 induction coil apparatus consisted of two insulated coils called the primary and secondary windings both placed around a common iron core. A battery intermittently connected to the primary would ‘induce’ a voltage in the longer secondary causing a spark to jump across its free terminals.
In an induction coil or electrical transformer, which can have either an iron core or an air core, the transmission of energy takes place by simple electromagnetic coupling through a process known as mutual induction. With this method it is possible to transmit and receive energy over a considerable distance. However, to draw significant power in that way, the two inductors must be placed fairly close together. If resonant coupling is used, where inductors are tuned to a mutual frequency, significant power may be transmitted over a range of many meters. In 1864 James Clark Maxwell mathematically modeled the behavior of electromagnetic radiation.
Some early work in the area of energy transmission via radio waves was done in 1888 by Heinrich Hertz who performed experiments that validated Maxwell’s mathematical model. Hertz’s apparatus for generating electromagnetic waves is generally acknowledged as the first radio transmitter. A few years later Guglielmo Marconi worked with a modified form of the Hertz-wave transmitter, the main improvement being the addition of an elevated conductor and a ground connection. Both of these elements can be traced back to the 1749 work of Benjamin Franklin and that of Mahlon Loomas in 1864. Nikola Tesla also invented radio transmission and reception but unlike Marconi, Tesla designed his own transmitter — one with power-processing capability some five orders-of-magnitude greater than those of its predecessors.
He would use this same coupled-tuned-circuit oscillator to implement his conduction-based energy transmission method as well. Both of these no-cables methods employ a minimum of four tuned circuits, two at the transmitter and two at the receiver. As wireless technologies were being developed during the early 1900s, researchers further investigated these different transmission methods. The goal was simply to generate an effect locally and detect it at a distance. Around the same time, efforts began to power more significant loads than the high-resistance sensitive devices that were being used to simply detect the received energy.
2. EVOLUTION OF WITRICITY
2.1 INVENTORS OF WITRICITY
The inventors of Witricity are the researchers from the team from Massachusetts Institute of Technology. They are the people who had coined the phrase of Witricity and this invention can change the way electricity is used today. With Witricity, the tangle of cables, plugs and charters that normally clutter homes can be rid of. Prof. Marin Soljacic provided the inspiration for the experiment and invention of Witricity. It was while standing in the kitchen one night, that on staring at his mobile phone that he had thought it would be nice if his mobile phone would take care of its own charging instead of him having to periodically charge it.
He then tried out his experiment using two coils of copper, where one was connected to a receiver, and the other to a transmitter. With the help of these two coils of copper, the inventors of Witricity managed to transmit power across seven feet through the air to instantly light up a light bulb. Though Witricity worked only distances up till 9 feet at its inception, the inventors believed that it was possible to charge a battery that was located at a distance of a few yards from the power source that was connected to the receiving coil. They state that it would be sufficient to place a source in each room to provide power to the whole house.
2.2. BIRTH OF WITRICITY TECHNOLOGY
The experimental design consisted of two copper coils, each a self-resonant system. One of the coils, connected to an AC power supply, was the resonant source. The other coil, the resonant capture device, was connected to a 60 watt light bulb. The power source and capture device were suspended in mid-air with nylon thread, at distances that ranged from a few centimeters to over 2.5 meters (8.2 ft). Not only was the light bulb illuminated, but the theoretical predictions of high efficiency over distance were proven experimentally. By placing various objects between the source and capture device, the team demonstrated how the magnetic near field can transfer power through certain materials and around metallic obstacles. Thus Prof. Soljacic’s dream of finding a method to wirelessly connect mobile electric devices to the existing electric grid was realized. Witricity Corp. was soon launched to carry this technology forward from the MIT laboratories to commercial production.
2.3. FUNDAMENTALS OF WITRICITY TECHNOLOGY
Witricity technology is transferring electric energy or power over distance without wires with the basics of electricity and magnetism, and work our way up to the wireless technology.
The flow of electrons (current) through a conductor (like a wire), or charges through the atmosphere (like lightning).A convenient way for energy to get from one place to another!
A fundamental force of nature, which causes certain types of materials to attract or repel each other Oscillating magnetic fields vary with time, and can be generated by alternating current (AC) flowing on a wire. The strength, direction, and extent of magnetic fields are often represented and visualized by drawings of the magnetic field lines.
Fig.1 Magnetic Induction
A term for the interdependence of time-varying electric and magnetic fields. For example, it turns out that an oscillating magnetic field produces an electric field and an oscillating electric field produces a magnetic field.
A loop or coil of conductive material like copper, carrying an Alternating current (AC), is a very efficient structure for generating or capturing magnetic field. If a conductive loop is connected to an AC power source, it will generate an oscillating magnetic field in the vicinity of the loop A second conducting loop, brought close enough to the first, may “capture” some portion of that oscillating magnetic field, which in turn, generates or induces an electric current in the second coil. The current generated in the second coil may be used to power devices.
Energy coupling occurs when an energy source has a means of transferring energy to another object. One simple example is a locomotive pulling a train car—the mechanical coupling between the two enables the locomotive to pull the train. Magnetic coupling occurs when the magnetic field of one object interacts with a second object and induces an electric current in or on that object. In this way, electric energy can be transferred from a power source to a powered device.
Fig.2 Illustration showing resonance
Resonance can be thought of as the natural frequency at which energy can most efficiently be added to an oscillating system. A playground swing is an example of an oscillating system involving potential energy and kinetic energy.
Resonant Magnetic Coupling:
Magnetic coupling occurs when two objects exchange energy through their varying or oscillating magnetic fields. Resonant coupling occurs when the natural frequencies of the two objects are approximately the same.
Fig.3 Illusration showing the working of WiTricity
3. HOW WITRICITY TECHNOLOGY IS DIFFERENT THAN OTHER TECHNOLOGIES.
3.1. TRADITIONAL MAGNETIC INDUCTION
Witricity technology for power transfer appears to be traditional magnetic induction, such as is used in power transformers, where conductive coils transmit power to each other wirelessly, over very short distances. In a transformer, an electric current running in a sending coil (or “primary winding”) induces another current in a receiving coil (or “secondary winding”). The two coils must be very close together, and may even overlap, but the coils do not make direct electrical contact with each other.
However, the efficiency of the power exchange in traditional magnetic induction systems drops by orders of magnitude when the distance between the coils becomes larger than their sizes. In addition to electric transformers, other devices based on traditional magnetic induction include rechargeable electric toothbrushes, and inductive “charging pads” which require that the object being charged be placed directly on top of, or very close to, the base or pad supplying the power. The power exchange efficiency of some induction systems is improved by utilizing resonant circuits. These so called resonantly enhanced induction techniques are used in certain medical implants and high-frequency RFids.
Witricity founding technical team was the first to discover that by specially designing the magnetic resonators, one could achieve strong coupling and highly efficient energy exchange over distances much larger than the size of the resonator coils, distances very large compared to traditional schemes.
3.2. WITRICITY TECHNOLOGY IS DIFFERENT THAN RADIATIVE POWER TRANSFER
Witricity technology for power transfer is non-radiative and relies on near-field magnetic coupling. Many other techniques for wireless power transfer rely on radiative techniques, either broadcasted or narrow beam (directed radiation) transmission of radio, or light waves. Broadcasted radiation of radio frequency energy is commonly used for wireless information transfer because information can be transmitted over a wide area to multiple users. The power received by each radio or wireless receiver is miniscule, and must be amplified in a receiving unit using an external power supply.
Because the vast majority of radiated power is wasted into free space, radio transmission is considered to be an inefficient means of power transfer. Note that while more energy can be supplied to the receiver by “cranking up the power” of the transmitters in these systems, such high power levels may pose a safety hazard and may interfere with other radiofrequency devices.
Directed radiation”, using highly directional antennas, is another means of using radio transmission to beam energy from a source to a receiver. However, directed radiation—in particular microwave radiation—may interact strongly with living organisms and certain metallic objects. Such energy transfer methods may pose safety hazards to people or objects that obstruct the line-of-sight between the transmitter and receiver. These limitations make directed radio transmission impractical for delivering substantial levels of wireless power in a typical consumer, commercial, or industrial application. In fact, defense researchers are exploring the use of directed energy systems to deliver lethal doses of power to targets in space and on the battlefield.
3.3. WITRICITY TECHNOLOGY IS DIFFERENT THAN MAGNETIC RESONANCE IMAGING (MRI)
MRI machines use “magnetic resonance imaging” to produce diagnostic images of soft tissue. Many people assume that Witricity “Resonant Magnetic Coupling” must be similar to magnetic resonance imaging (MRI) technology, however, the technologies are similar in name only.MRI is, as its name suggests, a technology for using magnetism as a basis for diagnostic imaging of soft tissue in the human body. It utilizes a strong DC magnet to orient the magnetic fields of atoms within tissues, and radio frequency fields to manipulate those atoms in a selective way, so that tissues and structures can be imaged clearly. The “resonance” referred to in “MRI” refers to the resonance of atomic structures. MRI is not considered to be a method for wireless power transfer.
4. STRIKING FEATURES OF WITRICITY
4.1. HIGHLY RESONANT STRONG COUPLING PROVIDES HIGH EFFICIENCY OVER DISTANCE
Witricity mode of wireless power transfer is highly efficient over distances ranging from centimeters to several meters. Efficiency may be defined as the amount of usable electrical energy that is available to the device being powered, divided by the amount of energy that is drawn by the Witricity source. In many applications, efficiency can exceed 90%. And Witricity sources only transfer energy when it is needed. When a Witricity powered device no longer needs to capture additional energy, the Witricity power source will automatically reduce its power consumption to a power saving “idle” state.
4.2. ENERGY TRANSFER VIA MAGNETIC NEAR FIELD CAN PENETRATE AND WRAP AROUND OBSTACLES
The magnetic near field has several properties that make it an excellent means of transferring energy in atypical consumer, commercial, or industrial environment. Most common building and furnishing materials, such as wood, gypsum wall board, plastics, textiles, glass, brick, and concrete are essentially “transparent” to magnetic fields—enabling Witricity technology to efficiently transfer power through them. In addition, the magnetic near field has the ability to “wrap around” many metallic obstacles that might otherwise block the magnetic fields.WiTricity applications engineering team will work with you to address the materials and environmental factors that may influence wireless energy transfer in your application
4.3. NON-RADIATIVE ENERGY TRANSFER IS SAFE FOR PEOPLE AND ANIMALS
Witricity technology is a non-radiative mode of energy transfer, relying instead on the magnetic near field. Magnetic fields interact very weakly with biological organisms—people and animals—and are scientifically regarded to be safe. Professor Sir John Pendry of Imperial College London, a world renowned physicist, explains:“The body really responds strongly to electric fields, which is why you can cook a chicken in a microwave .But it doesn’t respond to magnetic fields. As far as we know the body has almost zero response to magnetic fields in terms of the amount of power it absorbs.” Evidence of the safety of magnetic fields is illustrated by the widespread acceptance and safety of household magnetic induction cook tops.
Through proprietary design of the Witricity source, electric fields are almost completely contained within the source. This design results in levels of electric and magnetic fields which fall well within regulatory guidelines. Thus Witricity technology doesn’t give rise to radio frequency emissions that interfere with other electronic devices, and is not a source of electric and magnetic field levels that pose a risk to people or animals. Limits for human exposure to magnetic fields are set by regulatory bodies such as the FCC, ICNIRP, and are based on broad scientific and medical consensus. Witricity technology is being developed to be fully compliant with applicable regulations regarding magnetic fields and electromagnetic radiation.
4.4. SCALABLE DESIGN ENABLES SOLUTIONS FROM MILL WATTS TO KILOWATTS
Witricity systems can be designed to handle a broad range of power levels. The benefits of highly efficient energy transfer over distance can be achieved at power levels ranging from mill watts to several kilowatts. This enables Witricity technology to be used in applications as diverse as powering a wireless mouse or keyboard (mill watts) to recharging an electric passenger Vehicle (kilowatts).Witricity technology operates in a “load following” mode, transferring only as much energy as the powered device requires.
4.5. FLEXIBLE GEOMETRY ALLOWS WITRICITY DEVICES TO BE EMBEDDED INTO OEM PRODUCTS
Witricity technology is being designed so that it can be easily embedded into a wide variety of products and Systems. The physics of resonant magnetic coupling enables Witricity engineers to design power sources and devices of varying shapes and sizes, to match both the packaging requirements and the power transfer requirements in a given OEM application. Witricity has designed power capture devices compact enough to fit into a cell phone
5. ADVANTAGES & DISADVANTAGES
No need of line of sight – In witricity power transmission there is no need of line of sight between transmitter and receiver. That is power transmission can be possible if there is any obstructions like wood, metal, or other devices were placed in between the transmitter and receiver. There’s no need of power cables and batteries – Witricity replaces the use of power cables and batteries. Does not interfere with radio waves and overall Wastage of power is small – Electromagnetic waves would tunnel, they would not propagate through air to be absorbed or dissipated.
So the wastage is small. Negative health implications – By the use of resonant coupling, wave lengths produced are far lower and thus make it harmless. Highly efficient than electromagnetic induction – Electromagnetic induction system can be used for wireless energy transfer only if the primary and secondary are in very close proximity. Resonant induction system is one million times as efficient as electromagnetic induction system. Its less costly – The components of transmitter and receivers are cheaper. So this system is less costly.
Wireless power transmission can be possible only in few meters. Efficiency is only about 40%.As witricity is in development stage, lot of work is done for improving the efficiency and distance between transmitter and receiver.
6. WITRICITY APPLICATIONS
Witricity wireless power transfer technology can be applied in a wide variety of applications and environments. The ability of our technology to transfer power safely, efficiently, and over distance can improve products by making them more convenient, reliable and environmentally friendly Witricity technology can be used to provide:
6.1. DIRECT WIRELESS POWER
When all the power a device needs is provided wirelessly, and no batteries are required. This mode is for a device that is always used within range of its Witricity power source.
6.2. AUTOMATIC WIRELESS CHARGING
When a device with rechargeable batteries charges itself while still in use or at rest, without requiring a power cord or battery replacement. This mode is for a mobile device that may be used both in and out of range of its Witricity power source. Witricity technology is designed for Original Equipment Manufacturers (OEM’s) to embed directly in their products and systems.
Witricity technology will make your products:
1) No manual recharging or changing batteries.
2) Eliminate unsightly, unwieldy and costly power cords.
3) Never run out of battery power.
4) Reduce product failure rates by fixing the ‘weakest link’: flexing wiring and mechanical interconnects.
5) More Environmentally Friendly:
6) Reduce use of disposable batteries.
7) Use efficient electric ‘grid power’ directly instead of inefficient battery charging
6.3. CONSUMER ELECTRONICS
Automatic wireless charging of mobile electronics (phones, laptops, game controllers, etc.) in home, car, office, Wi-Fi hotspots while devices are in use and mobile.
Fig.4 Electronic devices that can be powered up using Witricity.
Direct wireless powering of stationary devices (flat screen TV’s, digital picture frames, home theater accessories, wireless loud speakers, etc.) … eliminating expensive custom wiring, unsightly cables and “wall-wart” power supplies. Direct wireless powering of desktop PC peripherals: wireless mouse, keyboard, printer, speakers, display, etc… eliminating disposable batteries and awkward cabling. Industrial:
Direct wireless power and communication interconnections across rotating and moving “joints” (robots, packaging machinery, assembly machinery, machine tools) … eliminating costly and failure-prone wiring. Direct wireless power and communication interconnections at points of use in harsh environments (drilling, mining, underwater, etc.) where it is impractical or impossible to run wires.
Automatic wireless charging for future hybrid and all-electric passenger and commercial vehicles, at home, in parking garages, at fleet depots, and at remote kiosks. Direct wireless power interconnections to replace costly vehicle wiring harnesses and slip rings.
6.5. OTHER APPLICATIONS
Direct wireless power interconnections and automatic wireless charging for implantable medical devices (ventricular assist devices, pacemaker, defibrillator, etc.) Automatic wireless charging and for high tech military systems (battery powered mobile devices, covert sensors, unmanned mobile robots and aircraft, Direct wireless powering and automatic wireless charging of smart cards. Direct wireless powering and automatic wireless charging of consumer appliances, mobile robots, etc.
Fig.5 Illustration showing Witricity
Witricity engineering is often a non-radiative method of power switch, relying as an alternative within the magnetic close to field. Magnetic fields work together extremely weakly with organic organisms—people and animals—and are scientifically considered to get safe. WiTricity merchandise are becoming designed to comply with applicable security requirements and regulations. Therefore witricity is know-how safe. Witricity can switch energy is dependent to the supply and receivers. if it really is comparatively shut to one yet another, and may exceed 95%.Efficiency is mostly determined through the length amongst the ability supply and seize machine, about the other hand, the form may perhaps affect the efficiency. it may switch the facility by means of walls also.
Conventional magnetic induction calls for that the ability resource and seize unit be quite near to one a lot more typically inside millimeters to exchange ability efficiently. Witricity Technology is depending on sharply resonant sturdy coupling, and is particularly capable to exchange strength effectively even in the event the distances amongst the ability supply and seize gadget are many occasions the dimension of your products themselves.
8. FUTURE SCOPE
MIT’s Witricity is only 40 to 45% efficient and according to Soljacic, they have to be twice as efficient to compete with the traditional chemical batteries. The team’s next aim is to get a robotic vacuum or a laptop working, charging devices placed anywhere in the room and even robots on factory floors .The researchers are also currently working on the health issues related to this concept and have said that in another three to five years time, they will come up with a Witricity system for commercial use. TROY, Mich. — Delphi Automotive has reached an agreement with Witricity Corp., a wireless energy transfer technology provider, to develop automatic wireless charging products for hybrid and electric vehicles. The collaboration between the two companies will help establish a global infrastructure of safe and convenient charging options for consumer and commercial electric vehicles. “This is groundbreaking technology that could enable automotive manufacturers to integrate wireless charging directly into the design of their hybrid and electric vehicles,” said Randy Sumner, director, global hybrid vehicle development, Delphi Packard Electrical/Electronic Architecture.
“Delphi’s expertise in global engineering, validation and manufacturing coupled with Witricity patented wireless energy transfer technology uniquely positions us to make wireless charging of electric vehicles a reality.” Sumner said the wireless charging system would involve no plugs or charging cords. Drivers would simply park their electric vehicle over a wireless energy source that sits on the garage floor, or is embedded in a paved parking spot. The system will automatically transfer power to the battery charger on the vehicle. According to Eric Giler, chief executive officer, Witricity, their wireless system can already transfer over 3,300 watts — enough to fully charge an electric car at the same rate as most residential plug-in chargers. “Charging an electric car should be as easy as parking it in your garage or parking spot,” Giler said.
“Witricity high efficiency wireless energy transfer technology is ideally suited for electric vehicle charging, and our partnership with Delphi will help to quickly get this technology deployed in OEM vehicles and infrastructure projects worldwide.” Delphi can bridge the gap between the laboratory and the highway by providing E/E systems integration expertise, a global manufacturing and engineering footprint and high-voltage, high-power components specifically engineered for the hybrid and electric vehicles of today and tomorrow,” Sumner said.
Wireless charging technology will need to co-exist with plug-in charging solutions, Sumner added, so that electric vehicle drivers have the ability to charge their vehicle when they are away from their wireless charging source. Delphi also makes a Portable Electric Vehicle Charger that fits conveniently in the trunk of an electric vehicle. The user-friendly, UL-listed charging system plugs into any standard 120-volt outlet to enable safe electric vehicle battery charging at home or away. The charging unit can also be integrated into stationary charging applications.
Fig.6 Delphi’s solution for charging the cars using witricity technology
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